Gas turbine



La ALFoRD As TURBINEY Sept. 4, 1945.

Filed Jan. 22, 1943 Figi..

l Il I. lIM/evwtor". Joseph 5. Alford,

' a. is Pdztolfney.v

structure being attached to the nozzle wheel from direct and also to 'convey heat away from the wheel.

Patented Sept. 4, 1945 Joseph S. Alford, Nahan eral York t, Mass., assignor toGen- Electric Company, a corporation of New Application January 22, 1943, Serial No. 473,201

Claims.

'I'he present invention relates to gas turbines. It is especially .useful in connection with turbosuperchargers for aircraft wherein the turbine is operated by exhaust gases from an internal combustion engine. It is this application of my invention which I have elected to illustrate and describe. It is to be understood, however, that this is only by way of example andl that the invention may be used wherever found applicable.

In connection with turbosuperchargers for aircraft, it is known to provide on the discharge side of the turbine wheel a unitary structure comprising a iighthood and a cooling cap, the unitary box by suitable brackets in a manner such that the structure can be adjusted relatively to the turbine wheel to adjust the clearance between the edge of the cooling capl and the rim of the' turbine wheel, it being desirable to have close clearance between these parts.

The function of a iiighthood is to provide an exhaust chamber which receives the gases discharged from the turbine wheel, turns them, and directs them, in the case of an aircraft, into the slip stream. The purpose of the cooling cap is to protect the hub, web and rim ofthe turbine contact with hot exhaust gases In the case of an aircraft, the cooling cap is arranged usually to, provide a cooling chamber through which air from the slip stream of the aircraft is circulated.

In certain applications, it is important that air be prevented from leaking into and becoming mixed with the gases discharged from the turbine buckets as this 'results in the burning of any unconsumed fuel in after-burning.

One of the problems met with in the use of a structure comprising cooling cap is to provide a connection between it and the nozzle box for supporting it in a manner such that one may be adjusted relatively to the'other and at the same time prevent air from leaking into the exharust gas chamber defined by the flighthood.

An object of my invention is to provide in a gas turbine an improved arrangement for sup-v porting such-.a structure which permits of the neededrelative adjustment of the respective parts and at the same time prevents effectively leakage of air into the gases, and for a consideration of what I believe to be novel and 'my invention. attention is directed to the following speciiicatlon and to the claims appended thereto.

the gases, termed usually a combmed nighthood and' In the drawing, Fig. 1 is asectional view of a gas turbine (in the present instance the gas turbine of a turbosupercharger) embodying my invention; Fig. 2 is a sectional view taken on line 2 2, Fig. 1, and Fig. 3 is a detail sectional view i on a larger scale.

Referring to the drawing, 5 indicates a bearing housing in which is located abearing, not shown, for the turbosupercharger shaft 6. Overhung on the end of shaft 6 and suitably attached -thereto is a turbine wheel comprising a hub 8, a y

web 9, a rim I 0 and a ring of b'uckets Il. Surrounding bearing housing 5 in spaced relation thereto is an annular nozzle box l2 which carries a ring of nozzles I3 which directexhaust gases from the nozzle box to the ring of turbine buckets. The inlet conduit of the nozzle box is indicated at I4. In the case of the usual turbosupercharger, there is provided also in connection with the nozzle box a waste conduit in which is located a waste gate valve for regulating the liow of.

exhaust gases to the turbine wheel. This is not shown in the present instance as it forms no part of my invention. It will be understood that in the case of a turbosupercharger the shaft 6 dicate the direction of air iiow toward the wheel and the arrows B indicate the direction of the air flow away from the wheel. Usually, the cooling air is takexi'from the slip stream of the aircraft, Iiowing down across the bearing housing.

to cool the bearing, thence along the entrance side of the wheel and out as indicated by the arrows B.

The construction so far described is a known one and is to be taken as typical of any suitable gas turbine.

At la is indicated a nighthooa for th turbinev wheel which defines an exhaust chamber I9 which receives the Bases issuing from the turbine bucketsv and directs them to the slip stream.

Carried by and forming a unitary structure with the i'lighthood is a cooling cap 40. Any suitable cooling cap structure may be utilized. In the present instance, there is shown a cooling cap similar to that disclosed and claimed in my ap- 2 pucauon serial, No. 439,405, med `april' rz, 1942,

and assigned to the same assignee as the present application. It comprises generally walls defining a cooling chamber to which cooling medium, for example air from an aircraft slip ing ring or Wall 22 and to which they may be attached by welding or the like. Ring 22 is providedhwith a ilange 23 which is attached to the nozzle box preferably by welding. For adjusting the cooling cap relatively to the turbine wheel, shims as indicated at 44 may be inserted between lugs 2I and ilanges 45 on brackets 20, these being the parts through which the bolts pass for attaching brackets to lugs 2i. The admission end 24 of theilighthood is spaced from the inner surface of ring 22 and is provided with a radially extending flange 25 having an axially extending lip 26 which has sliding engagement with the inner surface of ring V22. Brackets 2li are attached to the ilighthood at points well spaced from lip 26. Attached to admission end 24 by welding or the like is an annular ring 21 provided with a lip 28 which has sliding engagement with the inner surface o! ring 22 and defines with flange 25 an annular sealing chamber 29. In the wall of admission end 24 are spaced holes 30 which connect exhaust 'chamber I9 to sealing chamber 29. The sliding iit between lips 26 and 28 and the inner surface of ring or wall 22 permits these parts to move relatively to each other in case of any unequal expansion or contraction during operation; also it permits such relative movement when the cooling cap is adjusted to x the clearance between the cooling cap rim 43 and the wheel rim I0.

.Gases discharged from a turbine wheel have a radial component, i. e., they discharge not directly axially but at an outward angle of considerable magnitude. Holes 30 .are so located that, when the turbine is operating, gases discharged from the turbine buckets will strike the wall of admission end 24 and passing through holes 3l! build up a positive pressure in annular chamber 29. As a result. any leakage between the inner face of ring 22 and lip 26 will be in the vform of gases passing to atmosphere rather than air into the exhaust chamber I9.

My invention has especial utility in instances where a portion of'a'nozzle ring is blanked off as in the case of partial admission, that is, where the nozzles occupy less than 360, orin the case where a cruising valve is employed to render apart of a. nozzle ring inactive since this provides an inactive are adjacent to an active arc vwhereby the discharge of gases from the active arc has an elector action on the adjacent inactive arc thus creating a region of negative pressure into which air tends to leak."v ins valve which when partition wall 22 in the closed cooperates with a nozzle box to render in- A active the arc of nozzles located between the the wall. No holes 30 are cruising valve and provided in the portion o! wall arc between 'Wallav and valve 9i, i. e.,

24 adiacent to the the inac- In Fig-2, 3l indicates a cruistive arc, since the presence or such holes would tend to counteract the building up of positive pressure in chamber 29.

By my invention, leakage is reduced to a minimum and such leakage as does occur is that of gases out to the atmosphere. As a result, I prevent effectively leakage of air to the interior of the 'ighthood Broadly, accordingto my invention the end of the flighthood has a cylindrical wall portion 24 and side walls 25 and 21 which form an annular channel. The free ends of the side walls 25, 21 have a sliding fit with a cylindrical wall 22 concentrlcally spaced With the turbine wheel and securely sealed to the nozzle box. The annular sealing channel thus formed communicates through openings 3|! with the exhaust end of the turbine to set up in said channel a sealing pressure above that of the atmosphere. The sliding iit between the ilighthood and the nozzle box precludes the setting up of excessive stresses due to the high temperature of the gases during operation. In addition, the ilighthood is rigidly and adiustably supported on thenozzle box by means of brackets secured to intermediate portions of the ighthood, which portions are substantially axially spaced away from the nozzle box whereby the rigid support does not aiect the sliding llt between the end portion of the ighthood and the nozzle box.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider te represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a gas turbine, a turbine wheel, a illghthood, a wall surrounding the turbine wheel with which the entrance end of the fllghthood has a sliding fit, means defining a sealing chamber adjacent to engaging parts of said wall and flighthood, means comprising openings in the entrance endof the flighthood for supplying to said chamber gases exhausting from the turbine wheel to build up a positive pressure in said sealing chamber, and means for rigidly supporting an intermediate portion of the ilighthood.

2. In a gas turbine, a tur-binewheel, a flighthood, a wall surrounding the turbine wheel with which the entrance end of the nlghthcod has a sliding fit, means dening a sealing chamber adjacent to engaging parts of said wall and flighthood, a wall of said chamber being provided with openings through which gases exhausting from the turbine wheel may pass to the chamber to build up a positive pressure therein, and bracket means for securely fastening to the first-named wall circumferentially spaced portions of theV brackets attaching the ilighthood to the nozzle box, said brackets being secured to intermediate portions of the ighthood, means denning a sealing chamber between the end portion of the flighthood and the nozzle box for preventing escape of air into the flighthood, and means for supplying to said chamber gases exhausting from the turbinewheel to in the sealing chamber.

build up a positive pressure 4. In a gas turbine, a turbine wheel, an annular nozzle box for supplying gases to the wheel, an

axially extending ring carried by the nozzle box surrounding the wheel, a tlighthood the entrance end of which has a sliding fit with said ring, walls defining a sealing chamber adjacent to said entrance end and ring, means for supplying to said chamber gases exhausting from the turbine wheel to build up a positive pressure in said sealing chamber in order to preclude leakage of air from 4the atmosphere into the exhaust end of the turbine, and means securely supporting an intermediate portion of the iiighthood on'the nozzle bon. v 5. An exhaust gas operated aircraft turbine located on the discharge side of the wheel,v a iiighthood substantially enclosing the cooling cap for conducting exhaust-gases from the bucket wheel to atmosphere, and means for sealing the fiighthood to and supporting it on the nozzle box, said means comprising a cylindrical wall securely sealed to the nozzle box and concentrically surrounding the bucket wheel, a channel-shaped end portion formed by the ighthood having side walls forming sliding fit with said cylindrical wall, means including openings in the channel-shaped end portion for admittingexhaust gases from the turbine to the channel formed by said portion to set up a pressure in said channel above that of the atmosphere,.and means including brackets for securely supporting anl intermediate portion of the ighthood on the nozzle box. 

